As digital processing technologies in the wireless industry have advanced recently, digital logic has focused more on the receive and transmit chains of the wireless radio frequency integrated circuit (RFIC). In addition, the number of baseband modems available continues to increase and each of these has different specifications. Further, internal control of current RFIC receive and transmit gain is typically digital. Thus, the interface between the wireless terminal and the baseband modems has become more complicated, and development of RFICs is delayed by the additional step of matching analog parameters in the baseband modem with digital parameters in the RFIC.
A number of baseband modems use analog control of gain, and the voltage range on the gain pin of the RFIC is generally different from that of the baseband modems. Furthermore, the voltage range and the gain range of each baseband modem may vary. Thus, a variety of interface specifications must be supported to allow for multiple baseband modems to operate with a single RFIC. However, adapting analog control of gain to digital control typically requires significant software development for each target baseband modem. In addition, rewriting software to transfer gain via a serial port interface results in critical software impact on the terminal and may not even be possible because gain control is hardware-based for many modems. Therefore, there is a need in the art for an improved method of providing analog control of digital gain in the RFIC.